JPH1046250A - Production of nonoriented magnetic steel sheet excellent in magnetic property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of ridging without deteriorating the magnetic properties of a nonoriented silicon steel sheet. SOLUTION: A continuously cast slab of nonoriented silicon steel, which has a composition consisting of <=0.01% C, 0.05-3.5% Si, 0.1-4.0% Sol.Al, and the balance Fe with inevitable impurities and satisfying (Si+Al)<=5%, is heated to 950-1150 deg.C, and, at the time of roughing at hot rolling, rolling reduction of 15-50% is applied in a slab-width direction. Then, rolling reduction of 40-85% is applied in a thickness direction at the final pass, followed by finish rolling. The resultant hot rolled coil is subjected, after hot rolled plate annealing at 600-1100 deg.C or in the as-hot-rolled state, to cold rolling and then to continuous annealing at 700-1100 deg.C, by which the nonoriented silicon steel sheet, excellent in magnetic properties and free from ridging, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-oriented electrical steel sheet which is optimal for the core of a rotor or a stator of a high-speed motor and has excellent magnetic properties with little ridging.

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets are used for rotor cores of electric motors and cores of transformers. In recent years, with the progress of inverters, the number of electric motors used in the high-frequency region exceeding 100 Hz has increased. Demand for steel plates with small losses is increasing. To reduce iron loss, it is effective to add elements such as Si and Al that increase the electrical resistance of steel. However, these elements are ferrite forming elements, and in the region of C: 0.01% or less, (Si + Al ): When the content is 1.5% or more, the steel becomes a ferrite single phase, and the solidified structure (columnar crystal) formed by continuous casting is hot-rolled without transformation, and subsequently subjected to hot-rolled sheet annealing and cold rolling. It is known that a defect called ridging occurs in which traces of columnar crystals are undulated in a line parallel to the rolling direction on the surface of the steel sheet. The non-oriented electrical steel sheet in which ridging has occurred not only impairs the commercial value in appearance, but also inevitably decreases the space factor when formed into a laminated iron core or the like.

[0003] As a method of preventing the ridging described above, the ridging is relaxed by annealing and recrystallizing a hot-rolled sheet for a long time. However, ridging caused by columnar crystals generated by continuous casting has been used. Not valid for
Further, a method has been proposed in which a small amount of elements such as Ti and Zr are added to reduce columnar crystals during continuous casting to increase equiaxed crystals and reduce ridging (Japanese Patent Publication No. 53-21994). However, the magnetic properties are deteriorated, which is not practical.

As another method for preventing ridging, for example, an unsolidified molten steel is agitated by electromagnetic force during continuous casting, and a slab center region corresponding to a non-recrystallization center region at the time of hot rolling determined by hot rolling conditions is determined. To reduce ridging by equiaxed crystallization in the range (JP-B-57-159)
No. 69), the final pass of rough rolling in hot rolling is 900 ° C.
A method in which the ridging of the product plate is eliminated by ending the rolling under the high-pressure rolling of 50 to 70% and finishing the subsequent finishing rolling in the low temperature region of 850 to 720 ° C (Japanese Patent Publication No. Sho 56-43091). In addition, the inclusion of impurities in steel is suppressed as much as possible, and for at least one of Ti and Zr, according to the total amount of Si and Al, {Ti (%) + 0.5Zr (%)} ≦ 0.022 / ｛ S
A method has been proposed in which ridging is suppressed by reducing i (%) + Al (%)｝ within a limit range (JP-B-56-31846).

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Publication No. 57-15 / 1982
According to the method disclosed in Japanese Patent No. 969, it is extremely difficult to produce a 100% equiaxed slab, and it is impossible to completely eliminate ridging in a continuous cast slab in which columnar crystals remain. Further, the method disclosed in Japanese Patent Publication No. Sho 56-43091 does not completely eliminate ridging. Furthermore, the method disclosed in Japanese Patent Publication No. 56-31846, like the method disclosed in Japanese Patent Publication No. 53-211994, causes deterioration of magnetic characteristics and is not practical.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a non-oriented electrical steel sheet having excellent magnetic properties which can eliminate ridging without deteriorating the magnetic properties by solving the above-mentioned disadvantages of the prior art.

[0007]

Means for Solving the Problems The present inventors have conducted various tests and studies to achieve the above object. As a result, by applying a predetermined amount of reduction in both the width direction and the thickness direction at a predetermined temperature during hot rough rolling, at the time of completion of rough rolling, columnar crystals of the continuous cast slab are destroyed and a recrystallized structure is generated. ,
It has been found that the temperature in this region does not cause deterioration of the magnetic properties, but rather improves. Furthermore, a predetermined Si + A
With respect to the amount of l, conventionally hot-rolled sheet annealing was necessary to prevent ridging, but it was determined that magnetic properties were good and ridging did not occur even without hot-rolled sheet annealing. Reached.

The method for producing a non-oriented electrical steel sheet having excellent magnetic properties according to claim 1 of the present invention is as follows: C: 0.01% or less;
i: 3.5% or less, Sol. Al: 4.0% or less, (Si + Al) is 5% or less, the balance is Fe and continuity casting slab of non-oriented electromagnetic steel consisting of unavoidable impurities,
Heat to 950 ° C or higher and 1150 ° C or lower, apply 15% or more and 50% or less reduction in the slab width direction at the time of rough rolling in hot rolling, and 40% or more and 85% in the thickness direction in the final pass.
The following reduction was applied, followed by finish rolling to form a hot-rolled coil, and after pickling, hot-rolled sheet annealing was performed at 600 ° C. or higher and 1100 ° C. or lower, or cold-rolled as hot rolled.
Finish annealing by continuous annealing is performed at 00 to 1100 ° C. As described above, after the hot-rolled coil of claim 1 is pickled, hot-rolled sheet annealing is performed at 600 ° C. or more and 1100 ° C. or less, or cold-rolled while hot-rolled,
By performing the finish annealing by continuous annealing at 1100 ° C., when the rough rolling of the hot-rolled coil is completed, the columnar crystals of the continuous cast slab are broken and a recrystallized structure is generated, so that ridging occurs during cold rolling. Thus, a non-riding non-oriented electrical steel sheet having excellent magnetic properties can be manufactured.

The method for producing a non-oriented electrical steel sheet having excellent magnetic properties according to claim 2 of the present invention is as follows: C: 0.01% or less;
i: 3.5% or less, Sol. Al: 4.0% or less, (Si + Al) is 5% or less, the balance is Fe and continuity casting slab of non-oriented electromagnetic steel consisting of unavoidable impurities,
Heat to 950 ° C or higher and 1150 ° C or lower, apply 15% or more and 50% or less reduction in the slab width direction at the time of rough rolling in hot rolling, and 40% or more and 85% in the thickness direction in the final pass.
A hot-rolled coil obtained by applying the following reduction and then finish rolling is subjected to hot-rolled sheet annealing at 600 ° C. or more and 1100 ° C. or less, or one or two or more intermediate annealings while hot-rolled. Cold-rolling is performed, and finish annealing by continuous annealing is performed at 700 to 1100 ° C. As described above, the hot-rolled coil according to claim 1 is used at a temperature of 600 ° C. or more and 1100 ° C.
Perform hot-rolled sheet annealing or
Cold rolling with intermediate annealing two or more times
By performing the finish annealing by continuous annealing at 0 to 1100 ° C., when the rough rolling is completed, the columnar crystals of the continuous casting slab are broken and a recrystallized structure is generated. A non-oriented electrical steel sheet without any ridging and having even better magnetic properties can be produced by intermediate annealing without generation.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the chemical components of steel in the present invention are as follows. C is 0.01%
If the content exceeds 0.1%, magnetic aging is caused and the magnetic properties are deteriorated.

[0011] Si is an essential element for improving magnetic properties, but if its content is less than 0.05%, its effect is not sufficient.
When the content exceeds 3.5%, the ductility is deteriorated, and troubles such as breakage of the rolled material during cold rolling are caused.
5% or more and 3.5% or less.

Sol. 3. Al is an important element for improving the magnetic characteristics. However, if it is less than 0.1%, fine AlN is generated, which conversely deteriorates the magnetic characteristics.
If added in excess of 0%, there is a risk of ignition or the like during hot rolling, so the content was set to 0.1% or more and 4.0% or less.

If the content of (Si + Al) exceeds 5%, the cold rollability is remarkably deteriorated.

The continuous cast slab of the above component is heated to a temperature of 950 ° C. or more and 1150 ° C. or less, and 15% or more and 50% or less in the slab width direction using a width reducing means such as a sizing press during rough rolling in hot rolling. And a reduction of 40% or more and 85% or less in the thickness direction in the final pass, followed by finish rolling to obtain a hot-rolled coil.

The heating temperature of the continuous casting slab is 950.
If the temperature is lower than 950 ° C., it is difficult to secure the finishing temperature, and the magnetic properties are deteriorated. If the temperature exceeds 1150 ° C., precipitates such as MnS in the steel are redissolved and the magnetic properties are deteriorated.
The temperature was set to 50 ° C. or less. Further, as shown in FIG. 1, the slab width reduction is essential for breaking columnar crystals, and if the width reduction ratio is less than 15%, there is no effect on ridging prevention, and if it exceeds 50%, width rolling becomes difficult. Therefore, the width reduction in the hot rough rolling is set to 15% or more and 50% or less. Further, the rolling reduction in the thickness direction in the final pass in hot rough rolling is 40%.
If it is less than 85%, there is no effect in preventing ridging, and if it exceeds 85%, rolling becomes difficult. Therefore, the rolling reduction in the thickness direction in the final pass in rough rolling is set to 40% or more and 85% or less.

After the hot rolled coil is pickled,
Hot-rolled sheet annealing at a temperature of not less than 1 ° C. and not more than 1100 ° C., or cold-rolling as hot-rolled, or cold-rolling with one or two or more intermediate annealings sandwiched, 700 to 1100
Perform final annealing by continuous annealing at ℃. The annealing temperature of the hot-rolled sheet is ineffective at less than 600 ° C., and when it exceeds 1100 ° C., the crystal grains become coarse, causing troubles such as breakage of the rolled material during cold rolling. did. If the intermediate annealing temperature in the cold rolling is less than 600 ° C., there is no effect, and if it exceeds 1100 ° C., the crystal grains become coarse, causing troubles such as breakage of the rolled material. On the other hand, if the final annealing temperature of the continuous annealing is lower than 700 ° C., a sufficient recrystallized structure cannot be obtained, resulting in poor magnetic properties and 1100 ° C.
If the temperature exceeds 300 ° C., grain boundary oxidation occurs from the surface layer, and conversely, magnetic properties deteriorate.

The finish-annealed cold-rolled steel strip is coated with an inorganic or semi-organic insulating film on both sides depending on the application. The insulating film is not particularly limited as long as it is not affected by insulating varnish, transformer oil, machine oil, etc., and is not particularly limited, but is spray-coated with a resin or a mixture of a resin and an inorganic binder,
A film is formed on both sides of the steel strip by a roll coater, curtain flow coat, or the like.

[0018]

EXAMPLE Test No. 1 shown in Table 1 was used. Test Nos. 1 to 9 in which the chemical compositions of the steels of the present invention and * are out of the scope of the present invention. 1
A continuous cast slab having a thickness of 227 mm and a width of 1000 mm of comparative steels 0 to 21 was heated under the heating conditions shown in Table 2, and
After hot rolling was performed under the hot rolling conditions shown in Table 3 to obtain a hot-rolled coil having a thickness of 2.3 mm, as shown in Table 3, the hot-rolled sheet was annealed or pickled without annealing. After cold rolling under the conditions shown to form a cold-rolled steel strip having a sheet thickness of 0.50 mm, and then recrystallization annealing by continuous annealing at the finish annealing temperature shown in Table 3, acrylic resin emulsion on both sides of the cold-rolled steel strip, A 0.4 μm-thick insulating film made of magnesium chromate and boric acid was formed by a roll coater method. A test piece was collected from each of the obtained magnetic steel sheets, and was subjected to JIS.
25c according to the electrical steel sheet test method specified in C2550
The magnetic properties were evaluated using an m Epstein tester, and the ridging was evaluated by the surface waviness measured by the surface waviness measurement method specified in JIS B 0610 surface waviness. Table 4 shows the results. The sizing press was used for the width reduction in the hot rough rolling.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

As shown in Table 4, Test No. Examples 1 to 9 of the present invention are both JIS C25 in both iron loss and magnetic flux density.
Kind 50A2 specified by 52 non-directional electromagnetic steel strips
The requirements of 70 to 50A470 are satisfied. On the other hand, in Test No. C in which the content of C was out of the range of the present invention. In the comparative example of No. 10, the magnetic characteristics are deteriorated due to the magnetic aging. Test No. 1 in which the Si content exceeded the upper limit of the present invention. 11
In Comparative Example 2, cold rolling was impossible due to sheet breakage during cold rolling. Further, Sol. Test No. 1 in which the content of Al exceeds the upper limit of the present invention. In the comparative example of No. 12, fire occurred during hot rolling and hot rolling was impossible. Furthermore,
Test N where the continuous casting slab heating temperature exceeds the upper limit of the present invention
o. In the comparative example of No. 13, the iron loss was 4.
It is as large as 57 W / kg. Further, the test N in which the width reduction in the rough rolling during hot rolling is not more than the lower limit of the present invention.
o. Test No. 14 in which the thickness reduction rate in the comparative example of No. 14 and the final pass of the rough rolling was not more than the lower limit of the present invention. In the comparative example of No. 15, the undulation was about twice that of the example of the present invention, and the occurrence of ridging was remarkable. Further, in Test No. where Si + Al exceeds the upper limit of the present invention. In the comparative example of No. 16, cold rolling was not possible due to sheet breaking during cold rolling. Furthermore, the width of the rolling reduction in the rough rolling during the hot rolling is equal to or less than the lower limit of the present invention, and the thickness reduction in the final pass of the rough rolling is less than or equal to the lower limit of the present invention. Comparative Example No. 17 and Test No. 17 in which the continuous casting slab heating temperature exceeded the upper limit of the present invention and the thickness reduction rate in the final pass of rough rolling was not more than the lower limit of the present invention. In the comparative example of No. 18, the undulation was about twice or more than that of the example of the present invention, and the occurrence of ridging was remarkable. Test No. 1 in which the hot-rolled sheet annealing temperature exceeded the upper limit of the present invention. In Comparative Example 19, cold rolling was impossible due to sheet breakage during cold rolling. Further, the test No. 1 in which the finish annealing temperature exceeded the upper limit of the present invention. In Comparative Example No. 20, deterioration in magnetic properties was observed. Furthermore, in the test No. whose finishing annealing temperature is equal to or lower than the lower limit of the present invention. In Comparative Example No. 21, a defect in magnetic properties in which iron loss was significantly increased as compared with the present invention example was observed.

[0024]

According to the method for manufacturing a non-oriented electrical steel sheet according to the first aspect of the present invention, the continuous cast slab is heated to 950 ° C. or more and 1150 ° C.
5% or more in the slab width direction during rough rolling
The hot-rolled coil, which has been subjected to a reduction of 0% or less and a reduction of 40% or more and 85% or less in the thickness direction in the final pass, is pickled, and then annealed or hot-rolled at 600 ° C or more and 1100 ° C or less. By subjecting the steel sheet to cold rolling as it is and performing finish annealing by continuous annealing at 700 to 1100 ° C., a ridging-free magnetic steel sheet having excellent magnetic properties can be manufactured.

Further, in the method for producing a non-oriented electrical steel sheet according to claim 2 of the present invention, the continuous cast slab is heated to 950 ° C.
It is heated to 0 ° C or less, and at the time of rough rolling, a reduction of 15% or more and 50% or less is applied in the slab width direction, and a hot rolled coil applied with a reduction of 40% or more and 85% or less in the thickness direction in the final pass is pickled. Then, the hot-rolled sheet is annealed at 600 ° C. or more and 1100 ° C. or less, or is cold-rolled with one or two or more intermediate annealings as it is while hot-rolled, and is subjected to finish annealing by continuous annealing at 700 to 1100 ° C. This makes it possible to manufacture a ridging-free electrical steel sheet having even better magnetic properties.

[Brief description of the drawings]

FIG. 1 is a graph showing a range of a width reduction amount and a thickness reduction amount in a final pass in hot rough rolling according to the present invention.

Claims (2)

[Claims] 1. C: 0.01% or less, Si: 3.5% or less, Sol. Al: 4.0% or less, and (Si + Al)
Is 5% or less and the balance is Fe and unavoidable impurities.
Heating to 150 ° C or less, and applying a reduction of 15% or more and 50% or less in the slab width direction during rough rolling in hot rolling,
In the final pass, a reduction of 40% or more and 85% or less is applied in the thickness direction, followed by finish rolling to form a hot-rolled coil, hot-rolled sheet annealing at 600 ° C or more and 1100 ° C or less, or cold rolling as hot-rolled. A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, comprising performing finish annealing by continuous annealing at 700 to 1100 ° C. 2. C: 0.01% or less, Si: 3.5% or less, Sol. Al: 4.0% or less, and (Si + Al)
Is 5% or less and the balance is Fe and unavoidable impurities.
Heating to 150 ° C or less, and applying a reduction of 15% or more and 50% or less in the slab width direction during rough rolling in hot rolling,
A hot rolling coil obtained by applying a reduction of 40% or more and 85% or less in the thickness direction in the final pass and then finish rolling is 600
It is characterized by subjecting to hot-rolled sheet annealing at or above 1100 ° C or cold-rolling with one or two or more intermediate annealing steps in between while hot-rolling, and finish annealing by continuous annealing at 700 to 1100 ° C. A method for producing a non-oriented electrical steel sheet having excellent magnetic properties.